1. Field of the Invention
The invention relates to a communication station for contactless communication with suitably designed data carriers, which communication station has an antenna configuration, in which the antenna configuration has at least one antenna with at least one pole and also at least one antenna with at least one essentially closed loop.
2. Related Arts
In connection with a communication station as described above reference can be made to patent document U.S. Pat. No. 5,572,226 A. This patent document states that in a communication station one dipole antenna or two dipole antennas and also one loop antenna can be provided. Here the antennas are provided and arranged with fields essentially independent of each other and the antennas can be operated in temporal succession in multiplex mode for detection purposes in order to find the most effective antenna in each case and in this way achieve the best possible communication in subsequent communication mode. In the known solution however in such a communication mode between the communication station and a data carrier connected to the communication station, always only one antenna is active so that the communication quality is dependent on the structure and relative position of the antenna with which the communication is performed. Because of this circumstance it may occur that the most effective antenna is selected and put into operation for communication mode, but because of given communication conditions, only an unsatisfactory or insufficiently satisfactory communication quality is achieved.
It is an object of the invention to avoid the above problems and achieve an improved communication station in relation to the state of the art.
To achieve the above object in a communication station according to the invention the features according to the invention are provided so that a communication station according to the invention can be characterized as follows, namely:
A communication station for contactless communication with suitably formed data carriers, which communication station has an antenna configuration, in which the antenna configuration has at least one antenna with at least one pole and in which the antenna configuration has at least one antenna with at least one essentially closed loop and in which an antenna with at least one loop is loosely coupled electromagnetically to an antenna with at least one pole.
By provision of the features according to the invention it is achieved that between an antenna with at least one loop and an antenna with at least one pole such an electromagnetic coupling predominates that firstly no unacceptably high and disruptive influence exists between these two antennas and the electrical circuits co-operating with these antennas and produced independently of each other, but that also because of the loose electromagnetic coupling a positive influence is exerted by the one of the two said antennas on the other of the two said antennas, with the result that viewed overall in relation to the state of the art in which no loose electromagnetic coupling exists between at least two antennas of an antenna configuration in communication mode because only one antenna is always active, clearly improved communication behavior is achieved. In a communication station according to the invention in which a carrier signal is used for communicationxe2x80x94as has been known in itself for some timexe2x80x94advantageously only a relatively low carrier signal power is required, which is particularly favorable since no problems can occur with official disruptive radiation regulations as a result. Furthermore the advantage is achieved that because of the improved communication conditions, smaller communication coils can be used in the data carriers provided for communication with a communication station, which is advantageous with regard to miniaturization of such data carriers. In particular the measures according to the invention have proved advantageous if an antenna with at least one pole is used mainly as the transmitter antenna and an antenna with at least one loop, which is loosely coupled electromagnetically with the one-pole antenna, is used as the receiver antenna.
In a communication station according to the invention a loose electromagnetic coupling is possible in a relatively large coupling range, for example in a range between 0.01% and 50% to 60%. It has, however, proved advantageous if the electromagnetic loose coupling corresponds to a coupling factor k which is in a range between k=0.01% and k=30%. It has proved particularly advantageous here if the loose electromagnetic coupling corresponds to a coupling factor k which lies in the range from k=0.1% to k=5.0%. Under these conditions particularly good results were achieved in test studies.
In a communication station according to the invention, the antenna with at least one pole can be formed by a dipole antenna. It has, however, proved particularly advantageous if the antenna with at least one pole is formed by a monopole antenna. This is particularly advantageous because with the monopole antenna particularly favorable field patterns can be achieved in relation to the co-operaction with contactless communication data carriers.
In a communication station with a monopole antenna, the monopole antenna can be formed essentially L-shaped. It has however proved particularly advantageous if the monopole antenna is formed essentially U-shaped and has two leg sections and a web section connecting the two leg sections. Such a design, known in specialist circles as a rod antenna with roof capacitance, has proved particularly advantageous in view of particularly good communication properties, because with such a design a field pattern comparable to a curtain can be achieved, which guarantees reliable communication with data carriers moving through this curtain-like field pattern.
In a communication station with a U-shaped monopole antenna, the antenna with at least one essentially closed loop can be loosely electromagnetically coupled with the web section alone or with the web section and a leg section. It has however proved advantageous if the antenna with at least one essentially closed loop is loosely electromagnetically coupled with a leg section of the U-shaped monopole antenna. This is particularly advantageous in view of an exceptionally simple construction and in view of good reception properties for essentially vertically oriented data carriers, which occur often in practice for example when data carriers are carried by persons on their bodies.
The aspects described above and further aspects of the invention arise from the examples of embodiment described below and are explained using these examples of embodiment.